Hi Guy, Thanks for your comments. <<< I'm still puzzled as to the best way to go for nulling of pests, regarding diameter vs length proportions. Initially the "long and skinny" antennas such as in the SRF-T615 were praised for their nulling, but now the "stubby" FSLs appear to have the upper hand. >>> Guy, there's no doubt that the stubby, hard-wired FSL's have really created a new level of nulling capability-- in an entirely different league than the loopsticks or long ferrite rods that preceded them. There are two primary reasons for this. The new hard-wired FSL's are completely isolated away from the radio circuitry, and they have no variable tuning capacitor to upset their RF symmetry. They present a completely symmetrical RF coil for reception purposes, which can null out pest stations under laboratory-perfect conditions every time. All of the preceding antenna designs were limited either by surrounding radio circuitry, a variable tuning capacitor to upset the RF symmetry, or both. <<< I guess this is an unfair apples to oranges comparison (hollow FSL vs traditional solid rod antenna). To compare FSL to FSL then, are you finding better nulling the "stubbier" you make the antennas? >>> Yes, there is now no doubt that the shorter and stubbier a hard-wired FSL coil becomes, the greater its nulling capability will be-- so long as the RF design is completely isolated , and completely symmetrical. <<< Do you recall the large diameter, short rod FSLs that Kevin Schanilec built inside of Christmas wreath containers? I wonder if those models were excellent at nulling. I do remember that he did a lot of his testing indoors, which can screw up nulls and reception completely. High performance ferrite antennas CANNOT be reliably evaluated indoors! >>> All traditional FSL's (including Kevin's designs) have a variable tuning capacitor-- which is a distraction from a perfectly symmetrical RF reception pattern. The larger and clunkier the variable capacitor, the worse and worse the nulling capability gets. Long hookup wires to a variable cap also upset the symmetrical RF reception pattern, further reducing nulling capability. The new hard-wired FSL's avoid both issues completely-- with perfect symmetry and no variable tuning capacitor. By the way, all of the local pests except for 1450-KSUH have been nulled down into the noise. My guess is that the over-modulated KSUH is broadcasting on more frequencies than its fundamental, making it tough to null each one :-) 73, Gary
----- Original Message ----- From: "Guy Atkins" <d...@guyatkins.com> To: "Mailing list for the International Radio Club of America" <irca@hard-core-dx.com> Sent: Saturday, January 23, 2016 3:02:59 PM Subject: Re: [IRCA] "Science Fiction PL-380"-- Pest Control Version > > Gary, > I'm still puzzled as to the best way to go for nulling of pests, regarding diameter vs length proportions. Initially the "long and skinny" antennas such as in the SRF-T615 were praised for their nulling, but now the "stubby" FSLs appear to have the upper hand. Do you think the cylindrical (hollow) design of the FSLs changes the response to a groundwave pest station so that a high diameter-to-length ratio *FSL* nulls better than a *solid* rod with a high LENGTH-to-diameter ratio? I guess this is an unfair apples to oranges comparison (hollow FSL vs traditional solid rod antenna). To compare FSL to FSL then, are you finding better nulling the "stubbier" you make the antennas? Do you recall the large diameter, short rod FSLs that Kevin Schanilec built inside of Christmas wreath containers? I wonder if those models were excellent at nulling. I do remember that he did a lot of his testing indoors, which can screw up nulls and reception completely. High performance ferrite antennas CANNOT be reliably evaluated indoors! 73, Guy Atkins Puyallup, WA > > > > ---------- Forwarded message --------- > From: d1028g...@comcast.net > To: Mailing list for the International Radio Club of America < > irca@hard-core-dx.com> > Cc: > Date: Sat, 23 Jan 2016 13:40:28 +0000 (UTC) > Subject: [IRCA] > > "Science Fiction PL-380"-- Pest Control Version > Hello All, > > The first of the new hard-wired FSL models specifically designed to have > an unusually sharp nulling capability is now a reality. With a "short and > stubby" FSL design that emphasizes symmetry, isolation and a tidy RF > reception pattern, this model can put all of my semi-locals (Seattle and > Tacoma) down in the noise-- and even receive a few competing stations on > their fundamental frequencies. Using 22 of the commonly available Russian > surplus 62mm x 12mm x 4mm bars, this model is one of the "spinoff" versions > of the 3" Bar FSL PL-380 model (for which the 15-page "Heathkit-like" > construction article was posted at > http://www.mediafire.com/view/w0gcek56f6aq7kr/3_Inch_FSL_Tecsun_PL.doc > ), and has an FSL "sensitivity score" (coil diameter x ferrite length) of > 264-- pretty close to the 300 point score of the article version (with > 100mm ferrite bars). The advantage of this model is that there is a huge > supply of the Russian surplus 62mm ferrite bars, currently sold on eBay by > two different sellers. You can get 20 of them for $13-- including shipping > from Lithuania. > > Construction of this model is identical to the article version, except for > the FSL construction (which may be added as an addendum). All of the > construction parts are readily available, also. Unless you live practically > next door to a local pest, this "pest control" model should cut > your offenders way down to size. A photo of the new model is posted at > https://app.box.com/s/5r95oxc9v24vm9hbpe2w1g800lbt4d3b > > 73 and Good DX, > Gary DeBock (in Puyallup, WA, USA) > > > _______________________________________________ IRCA mailing list IRCA@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: irca@hard-core-dx.com _______________________________________________ IRCA mailing list IRCA@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: irca@hard-core-dx.com
